New K & N and air box mod....WOW

[Mr. Schweer]

Just changed the stock air filter out for a K & N and did the air box mod. Wow, what a difference. Obviously, I didn't just get another 15whp, but it did give my particular bike an enhancement. I put on a Kerker 4 into 1 a couple of weeks ago and noticed a loss in power below 3K.
When I pulled the airbox, the stock filter was filthy and nasty so I'm sure that even a stock type filter would've helped.
The best thing is that I've got back some of the low end. Now the power is back from about 2K on. Pulls much harder on the top end too.
Can't wait to get some new coils.

[T99Ford]

Everyone complains about the power below 3K with a 4-1 system. Most of the benefit of the 4-1 is from 5 and up, when you get the benefit of the scavenging, and after you have passed the HUGE midrange rich spot at 3-4K(unless you have jetted accordingly for that already...) It is amazing what a clean air filter will do.

[yamahansolo]

i have a kerker and i didn't notice any power loss with the rejett and pods. also if you look in the mods section on the exhaust it says the only exhaust to really make any gains was the kerker all other lost some power but they shaved alot of weight off the bike.

[T99Ford]

I didn't say power loss, just power complaint. All the 4-1's don't really do much taht the 4-2 didn't until after 5K, which is the way they work. They will all lose power at 3-5K until they are properly jetted, and then gain power at the top end. Hence the industry now makes 4-2-1 pipes instead of the 4-1 for most modern applications.

[Mr. Schweer]

Well I think I'm happy with the way it's running right now. I think I'm going to wait until I have upgraded the coils before re-jetting. Might check the float level though.
Better flowing exhaust really exposes the weakness of the intake side. The 4-2-1 is a much better idea than the 4-1, but mine came WITH the $175 '78 parts bike so the price is to hard to beat!!

[T99Ford]

But there is nothing wrong with the 4-1. It is designed to move your power band to the upper part of the RPM range, for more aggressive riding. The problem is that most people put the 4-1 on for more power, and then lug around town below 5K, complaining about how it runs. The 4-2-1 just smoothes the transition from low to higher RPM to negate the midrange re-fueling and exhaust dilution problems of the 4-1. It doesn't really add more power than the 4-1, just solves some of the transition issues of the 4-1.
Not to tell you what to do, but just a suggestion: Even with your stock coils (provided they are working properly now), do the jetting. I would recommend dyno jetting it so that you can graph your Air/Fuel ratio and tune for specific targets. Most likely your first run will show a lean idle, fat midrange, and lean top. Having read your other threads/ posts, you are looking to maximize performance. Most people that are tuning by "feel, ear, or seat of the pants", stop jetting tuning long before they reach the full potential, since they stop when everything starts running smoothly, not when it runs optimally. Different coils are probably not going to change your tuning results much if you have only done a pipe and air filter for engine mods, and you can start enjoying the benny's of the mods you've done now!

[Mr. Schweer]

Oops....shoulda clarified. This thread is regarding my sf not the e build up. I don't know if I NEED to rejet just yet. Not really looking for much more power with this bike, I'm pretty happy with it. I just want it to run to the best of its ability, you know?

[thewiz]

I'm about to go right there too, Mr Schweer ..

Already drilled the airbox and put in the K&N on my F. It's factory exhaust could be saved if I take it off and weld up a few holes and jet hot it NOW before it gets too rusty, AND, and nice a Kerker to put back in it's place. Ultimately, I prefer the factory exhaust for this bike though. Next weeks projects ... ho hum

[yamahansolo]

here is the faq taling about the exhaust...
it shows ther kerker 4-1 as the best. but it must be rejetted for optimal gains.

http://www.xs11.com/forum/showthread...hlight=exhaust

[T99Ford]

Yamahan: While I agree that the Kerker is the premium product, that looks more like someone's personal opinion, rather than dyno proven performance. But like the author said, how much performance is debatable, so we will leave it at that. The key to ANY performance gains from any 4-1 is the jetting more than the pipe. Unless the pipe is jetted correctly, you will see a performance loss (though maybe not real noticeable) until that problem is corrected. The person that invents the after market bolt on that makes 25% power with no changes will be a rich man indeed!
Schweer: Run it on a dyno. You might be surprised...But if you're happy and it runs good, ride on, Brutha!

[T99Ford]

Enough pipe talk! This is an airbox thread, and I don't even have an airbox

[thewiz]

Well, T71 ..

and I don't even have an airbox

I have a couple extra ... need one?
Hmmm, if not, maybe I'll try to make one into a birdhouse ???

[Mr. Schweer]

Wiz, my number one pipe was welded up by p.o. so close to the flange that you can't even move the collar off the studs! AND the weld looks like steven hawkings tried to do the repair with j.b. weld!!!! Same thing with where the right side muffler is welded on. Back in march is was cruising about 70 of the freeway and the bike started making so much noise I thought the engine was about to seize.....very scary. Turns out pipe number two had broken in two places INSIDE....didn't know there was pipe inside pipe. The actual I.d. of these pipes is TINY. Anyhow, got that 'fixed', but that only lasted a month. Plus it needed dents knocked out of it as well as being rechromed.
Its NO wonder 4-1s loose so much bottom end compared to stock.
I know carb work is in order, but plugs look decent after a full blast shutdown. Still though, I don't want to burn a piston due to laziness.....or more correctly, due to not wanting to catch fire!!!! Its been 100+• here the past few weeks and I just don't want to die working outside!!!
I'm going to weld in a wide band before I start monkeyin around with the carbs. I'd rather know just where I need to richen them up instead of guessing and having to pull them three or four times to get them right.

[thewiz]

Yup ... I haven't decided completely...

yet to restore these pipes ... once they're off, I should have a better idea. Don't want any of this though ... lol

steven hawkings tried to do the repair with j.b. weld!!!!